Ozone finds a wide variety of uses due to its very strong oxidant properties. Common uses for ozone include oxide film formation, e.g., semiconductor film formation, sterilization, and waste water treatment. A wide variety of methods have been proposed to generate ozone efficiently. The quantity of ozone produced by a given process or generator depends on a number of factors such as reactant gas concentration, electric power applied, temperature and gas flow rate.
Though a strong oxidant, ozone is not particularly stable and tends to decompose at elevated temperatures to reform diatomic oxygen. To achieve higher ozone concentrations, some propose to increase power density to the generator. While resulting in higher ozone concentrations, this approach requires significantly more power input and also results in higher system temperatures. As the temperature of the exit gas stream increases, so too does the decomposition of the ozone formed by the process.
Some form of cooling is typically used in the industry to withdraw unwanted heat produced during ozone generation. Cooling can be accomplished by varying the flow rate or flow path of the reactant gas through the generator. One example of this cooling method can be found in U.S. Pat. No. 4,213,838. Other gas driven cooling configurations include countercurrent flow of the reactant gas behind the dielectric members, as proposed in U.S. Pat. No. 5,008,087. However, the most common method for removing unwanted heat is the use of a fluid coolant, most often room temperature water. One example of water cooling is the jacket cooling arrangement described in U.S. Pat. No. 4,954,321.
U.S. Pat. No. 5,366,703 suggests that the efficient production of ozone can be accomplished using gas compression. This arrangement introduces a reactant gas into a generator at a pressure of between 1 and 3 bar and at a temperature of not greater than 50.degree. C. The gas is subjected to ozone generation and is then isothermally compressed to result in an ozone containing stream having a temperature not greater than the temperature of the feed gas and a pressure of at least 3 bar. This process however, suffers from the disadvantage that it requires both compression and cooling to obtain reasonable ozone concentrations.
The present invention overcomes the disadvantages of the prior art and produces higher ozone concentrations without the additional process of gas compression. Furthermore, the present invention improves the concentration of generated ozone by manipulating the temperature and concentration of the reactant gas.